Severe prenatal stress (administered to pregnant rats during the last week of gestation) has been reported to demasculinize and feminize the sexual behavior of male offspring. Attempts thus far (including one in my laboratory) to explain this phenomenon solely in terms of the nonspecific maternal hormonal response to stress have not been encouraging. Therefore, it is proposed to replicate the Ward stress procedure and then, by analyzing it into its component parts - i.e., pressure on the uterus, hyperthermia, disruption of circadian ryhthmicity, and postnatal maternal influences - discern which aspect affects male offspring sexual behavior. With this information, the next experiment will examine the role of maternal adrenal secretions in mediating the sexual behavior effect by applying the effective stressor to adrenalectomized or adrenal demedullated rats. In both experiments, additional male siblings will be given open field and cage emergence tests of emotional reactivity, traditional measures of prenatal stress effects. Since these behaviors are sexually dimorphic, behavioral feminization may extend to these behaviors as well as to sexual behavior.